The invention relates to antennas and, more particularly, to antennas which are compact in size while providing onmidirectional coverage with wide frequency bandwidth performance.
Small antennas capable of providing omnidirectional coverage over a wide frequency bandwidth have many aircraft and other applications. A previously described type of antenna utilizes a monopole element in the form of a flat faced planar disk of circular configuration, which is supported above a ground plane with its faces normal to the ground plane. Results of testing operational performance of such antennas are provided in an article by N. P. Agrawall, et al., titled “Wide-Band Planar Monopole Antennas”, in IEEE Transactions on Antennas and Propagation, vol. 46, No. 2, February 1998, pp. 294–295. Based on the test results, this article concludes that while broadband operation is achievable, the radiation pattern of the antenna is subject to degradation at the upper portion of the frequency band (i.e., with reference to a “bandwidth of 2.25–17.25 GHz” it is stated that “the pattern degrades above 12 GHz”). Thus, the form of flat disk antenna described in the article may not be capable of providing the wide frequency bandwidth performance required in some applications.
Objects of the present invention are to provide forms of antennas which are new or improved and which may provide one or more of the following capabilities or characteristics:                improved wideband performance via E-field enhancement;        third dimensional radiating element property for E-field enhancement;        dielectric material inclusion for E-field enhancement;        omni-directional antenna pattern;        wide frequency bandwidth;        suitable gain level uniformity over wide bandwidth; and        design flexibility to meet implementation requirements.        